Turnover and fate of 15N-labelled cattle slurry ammonium-N applied in the autumn to winter wheat

The fate of ¹⁵NH₄-N labelled cattle slurry applied before sowing in September of a winter wheat crop was studied on a loamy sand soil. The aim was to quantify immobilization of slurry NH₄-N into microbial biomass, the speed at which nitrate derived from the slurry NH₄-N was transported down the soil profile, and the utilization of slurry NH₄-N by the winter wheat crop. Cattle slurry was applied at a rate corresponding to 75 kg NH₄-N ha⁻¹ , with very little loss by volatilization (<4%) due to rapid incorporation by ploughing. The slurry amendment resulted in a doubling of soil surface CO₂ flux, an index of microbial activity, over non-amended soil within the first c. 2 weeks, but ceased again after c. 4 weeks, due to depletion of the easily degradable substances, e.g. volatile fatty acids, in the slurry. Nitrification of the applied NH₄-N was fast and complete by 3 weeks from application, and at this time, the maximum immobilization of slurry NH₄-N into the microbial biomass (23% of applied ¹⁵NH₄-N) was also observed, although no significant increase in total microbial biomass was observed. Rapid turnover of the microbial biomass quickly diluted the assimilated ¹⁵N, with only 6% of applied ¹⁵NH₄-N remaining in the microbial biomass by next spring. Downwards transport of nitrate was rapid in spite of lower than normal precipitation, and slurry-derived ¹⁵NO₃-N appeared in ceramic suction cups installed at 60 cm depth already 2 months after slurry application. Due to the unusually low winter precipitation in the experimental year, wheat yields were high, and the recovery of N in above-ground plant biomass derived from slurry NH₄-N at harvest reached 32%. An additional 45% of the applied slurry NH₄-N could be found in the soil to a depth of 100 cm (mostly in organic form in the plough layer), indicating that 23% had been lost by leaching or in gaseous form. It was concluded that although significant immobilization of slurry NH₄-N did occur, this was not sufficient to prevent leaching of slurry-derived N over the winter and that the relatively high recovery of slurry-derived N in the wheat crop was due partly to lower than normal winter percolation and partly to a relatively high rooting depth on this particular site.     

Time Course of Nitrogen in Soil Solution and Nitrogen Uptake in Maize Plants as affected by Form and Application Time of Fertilizer Nitrogen

Field experiments with silage maize were conducted in 1987 and 1988 on a loess-derived Luvisol in southwest Germany. Four nitrogen fertilizer treatments were compared: application of preplanting NH₄ N (plus a nitrification inhibitor, dicyandiamide as Didin) and preplanting NO₃-N, split application of NO₃-N (preplanting and side dressed 45 days after planting) and a control without nitrogen fertilizer in 1987 and with 64 kg N ha^?1 as calcium ammonium nitrate in 1988. The total amounts of soil mineral nitrogen (N_min+ fertilizer N) were 200 kg N ha^?1 in 1987 and 240 kg N ha^?1 in 1988. Suction cups and tensiometer were installed at five depths and samples were taken in regular intervals. Nitrate concentrations in the suction solution steeply increased at 15 cm and 45 cm soil depth 3-4 weeks after fertilizer application (1987 up to 160mgNl^?1; 1988 up to 170mgN l^?1) and steeply decreased up to 75 cm depth with the onset of intensive N uptake at shooting. Ammonium concentrations in the suction solution were very low (0-0.16 mg N l^?1). Compared to preplanting NCyN application, preplanting NH₄-N and split NO₃-N application decreased nitrate concentrations in the suction solution in spring 1987. In 1988, however, nitrate concentrations in the suction solution of preplanting NH₄-N and split NO₃-N application plots did not fall below 50mgNl^?1 at 15 cm depth during the growing season. Nitrate concentrations of split NO₃-N application increased again in autumn 1988 and hence doubled the calculated N losses by leaching during the winter months compared to preplanting N applications. At shooting, plants of the preplanting NH₄-N treatment had lower nitrate concentrations in leaf sheaths compared to plants of preplanting NO₃-N application. Total N uptake of maize between shooting and early grain filling of preplanting NH₄-N and split NO₃ -N application tended to be higher compared to preplanting NO₃-N application, reflecting the higher N availability in the soil later in the season. However, final dry matter yields and N uptake were not significantly affected by N form or time of N application. Since N losses by nitrate leaching between N application and onset of N uptake by plants were negligible on the experimental site, preplanting NH₄-N application and split NO₃-N application showed no agronomic advantages. High amounts of side dressed NO₃-N may increase nitrate leaching during the winter months, especially in years with delayed rainfall after application.     

不同氮素用量对黄瓜幼苗生长及养分吸收的影响

为确定黄瓜幼苗对氮素用量及氮素形态的响应特性以指导育苗期间合理施肥,以硝酸铵磷（NO3--N:NH4+-N为0.9:1.0）为供试肥料,研究同时提供NO3--N和NH4+-N的情况下,不同氮素用量对黄瓜幼苗生长及养分吸收的影响。结果表明：与不施氮对照相比,氮素施用可显著增加植株叶面积和株高,但各施氮处理之间差异不明显（50~200 mg N/株）;植株幼苗茎粗和地上部干物质累积量不同处理间差异不显著;施用氮素黄瓜幼苗根系的根长、根表面积和干物质累积量降低（尤其氮用量100 mg/株）,根系直径在0.5~1.3 mm和1.8~2.6 mm范围内的根长下降明显。氮素用量显著影响了地上部氮、磷、钾的浓度及吸收量,对根系的磷、钾浓度和氮、磷、钾的吸收量影响较小;综合地上部和根系的生长状况,氮素用量在50 mg/株及150 mg/株时,黄瓜幼苗的生长健壮。     

2种微生物菌剂对蔬菜花卉秸秆高温堆肥过程中氮变化的影响

为寻求蔬菜花卉秸秆简单、有效的利用方法,减少滇池流域农业面源污染。通过堆肥试验研究了蔬菜花卉秸秆接种微生物菌剂农冠和微元后,在翻堆和不翻堆2种处理方式下,高温堆肥过程中温度、全氮(T-N)、水溶性NH₄ -N和水溶性NO₃^--N含量随时间的变化规律。结果表明：不翻堆的3个处理由于缺氧,发酵速率低,短期内不易腐熟。翻堆处理中,纯物料对照样品升温过程缓慢,高温分解阶段持续时间短, T-N损失大,堆肥品质差;添加微生物菌剂农冠后,与纯物料对照相比,提前3天进入高温分解阶段,高温分解持续时间延长4天,T-N含量损失比对照低10.9%,水溶性NH₄ -N比对照降低24.7%,水溶性NO₃^--N则比对照增加14.0%;添加微生物菌剂微元后,与纯物料对照相比,提前5天进入高温分解阶段,高温分解持续时间延长6天,T-N含量损失比对照低24.1%,水溶性NH₄ -N比对照降低29.3%,水溶性NO₃^--N则比对照增加24.2%。接种微生物菌剂可促进水溶性NH₄ -N向水溶性NO₃^--N转化,降低堆肥容重,其中添加微元综合效果更理想。在翻堆条件下接种微生物菌剂微元可加快蔬菜花卉秸秆堆肥化进程,提高堆肥产品品质,且方法简单易行,适合在全流域进行广泛推广。     

尿素及秸秆添加对华中地区茶园土壤CO_2和N_2O排放的影响

为了明确尿素和秸秆添加对茶园土壤CO_2和N2O排放的影响,为茶园合理施肥提供理论依据,本研究在室内培养条件下,以华中地区红壤丘陵区茶园土壤为对象,运用静态培养系统研究方法,研究该土壤在尿素输入和作物秸秆添加后CO_2和N_2O的排放特征。培养试验共设置对照、尿素、作物秸秆和尿素+作物秸秆4种处理。结果表明:不同处理下华中地区茶园土壤CO_2和N_2O排放呈显著差异。作物秸秆添加显著提高茶园土壤CO_2的排放,作物秸秆和作物秸秆+尿素处理分别是对照的5.57和4.99倍。尿素输入显著促进茶园土壤N_2O的排放,而秸秆添加却降低N_2O的排放。对照和添加尿素处理土壤N_2O排放通量与铵态氮含量呈显著正相关关系。无秸秆添加处理土壤N_2O排放通量与硝态氮含量呈显著的相关性,而添加秸秆处理二者无显著相关关系。土壤可溶性有机碳含量对CO_2排放有显著影响,二者之间呈极显著线性正相关关系。     

甜菜亚硝酸还原酶基因(NiR)的克隆与表达分析

以甜菜品种甜研7号叶片的cDNA为模板,采用RT-PCR和3′/5′RACE技术,获得了编码亚硝酸还原酶基因(NiR)的cDNA全序列2 014 bp, 包含有1 830 bp的开放阅读框,编码599个氨基酸。所推导的氨基酸序列与菠菜及拟南芥NiR编码的氨基酸序列均具93%的同源性。生物信息学分析表明,甜菜NiR具有完整的NiR蛋白结构,含血红素蛋白β-化合物区域和4Fe-4S区域, 并利用分析软件预测其三维结构。实时荧光定量结果显示,在以0、10、20、30、40、50、80和160 mmol L^–1 NO₃^–-N处理72 h的试验中,50 mmol L^–1处理可使甜菜NiR的表达量达到最大;以0、2、4、8、16、32、64和128 mmol L^–1 NH₄⁺-N处理48 h的试验表明,8 mmol L^–1和64 mmol L^–1处理条件下甜菜NiR表达量相对较高。硝态氮和铵态氮不同配比处理48 h的试验中,NO₃^–-N和NH₄⁺-N比例为80:20可使甜菜NiR的表达量达到最大;在氮素诱导的基础上,蛋白抑制剂放线菌酮处理9 h,随着处理浓度的增大,NiR的表达量逐渐下降;不同浓度NO₂^–处理的试验中,40 mmol L^–1处理下NiR的表达量最大。     

浮床栽培鱼腥草对吉富罗非鱼养殖池塘水质的影响

为研究浮床栽培鱼腥草(0、5%、10%和15%种植面积)对吉富罗非鱼养殖池塘的水质净化作用,测定了NH_4+~-N、NO_3~--N、NO_2~--N、TN、TP、CODMn等主要水质指标。结果表明,在同样的试验条件下,7—8月份鱼腥草处理组NO_3~--N下降,与此同时带来了NH_4~+-N(除5%处理组)和NO_2~--N的上升。9月份浮床栽培鱼腥草对5种水质指标的平均去除率在3%~38%之间。5%鱼腥草种植面积适合进行中试。通过鱼腥草的采收,5%鱼腥草处理组叶、根茎的产量分别可达112.4、1619.2 kg/hm~2,且可从养殖水体带走0.38 g/m~2的总氮,0.06 g/m~2的磷元素;同时收获鱼总重和所测生物学指标(除体重)显著高于对照和其他处理组,且对成活率和饵料系数无多大影响。     

氮素形态及供应时期对马铃薯生长发育与产量的影响

选用马铃薯克新1号和费乌瑞它2个品种,于2013-2014年在沙培条件下,研究了氮素形态及供应时间对马铃薯植株生长、块茎形成及发育的影响。结果表明,在块茎形成前供应NO₃-N与NH₄-N两种条件下,马铃薯植株高度、叶面积、叶片SPAD值、整株干物质积累量以及块茎重量无显著差异,而块茎形成后供应NH₄-N的马铃薯叶片SPAD值、植株生长速度及块茎产量均显著高于NO₃-N处理;块茎形成前供应NO₃-N的植株结薯数显著高于NH₄-N处理,但是氮素形态对干物质在马铃薯块茎中的分配比例无显著影响。因此,马铃薯的氮素养分管理应根据商品薯和种薯生产的不同目标,在块茎形成前后分别供应适宜形态的氮素。     

Expression of <Emphasis Type="Italic">Bruguiera gymnorhiza</Emphasis><Emphasis Type="Italic">BgARP1</Emphasis> enhances salt tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis> plants

We have previously reported that expression of salt-responsive genes, including Bruguiera gymnorhiza ankyrin repeat protein 1 (BgARP1), enhances salt tolerance in both Agrobacterium tumefaciens and Arabidopsis. In this report, we further characterized BgARP1-expressing Arabidopsis to elucidate the role of BgARP1 in salt tolerance. BgARP1-expressing plants exhibited more vigorous growth than wild-type plants on MS plates containing 125–175 mM NaCl. Real-time PCR analysis showed enhanced induction of osmotin34 in the 2-week-old transformants under 125 mM NaCl. It was also showed that induction of typical salt-responsive genes, including RD29A, RD29B, and RD22, was blunted and delayed in the 4-week-old transformants during 24 h after 200 mM NaCl treatment. Ion content analysis showed that transgenic plants contained more K⁺, Ca²⁺, and NO₃ ⁻, and less NH₄ ⁺, than wild-type plants grown in 200 mM NaCl. Our results suggest that BgARP1-expressing plants may reduce salt stress by up-regulating osmotin34 gene expression and maintaining K⁺ homeostasis and regulating Ca²⁺ content. These results indicate that BgARP1 is functional on a heterogeneous background.     

添加硝酸钙对池塘沉积物中理化因子的影响研究

为减少池塘底泥对养殖水环境的影响,以硝酸钙和养殖池塘底泥沉积物为研究对象,采用模拟试验方法,探讨了添加硝酸钙对池塘沉积物理化因子的影响。结果表明：添加硝酸钙后,表层沉积物间隙水中NH₄⁺-N浓度持续降低,最终降至初始值的14.78%;同时可以显著降低表层和深层沉积物间隙水中的PO₄^3--P的浓度,在表层降低的幅度较大,第7~28天可降低超过85%的PO₄^3--P。试验结果表明,添加硝酸钙可以显著改善池塘底泥沉积物中NH₄⁺-N和PO₄^3--P的含量,研究结果对减少池塘底泥沉积物的修复具有积极的生态学意义。     

Model for Slurry and Manure in CERES and Similar Models

Proceeding from the structures and hypotheses of the CERES and SALUS models a model for considering manures has been developed. The model includes the following processes: infiltration during application, ammonia volatilization, leaching of ammonium and organic bound nitrogen and mineralization before incorporation, incorporation, ammonia volatilization, mineralization and leaching of organic bound nitrogen after incorporation. With the CERES Maize model combined with the manure model simulations were calculated concerning the following problems:
– influence of application time of slurry on nitrate leaching under German site conditions and
– influence of long-term slurry fertilization and of stopping slurry fertilization on organic N content, mineralization, uptake by maize and leaching under Southern Michigan site conditions.
Results and conclusions are presented.     

Long-term effects of N fertilization on cropping and growth of olive trees and on N accumulation in soil profile

Two experiments were conducted for 13 years in two olive groves of southern Spain to study the long-term effect of nitrogen (N) fertilization on trees and soil. In the first experiment, 12-year-old ‘Picual’ olive trees were arranged in a split plot design with method of N application (soil versus a 50% soil:50% foliar combination) as the whole plot factor, and amount of N applied annually (0, 0.12, 0.25, 0.5 or 1.0 kg N tree⁻¹) as the subplot factor. In the second experiment, N application to 50-year-old ‘Picual’ trees was based on the previous season's leaf N concentration. Urea was the source of N in both experiments. During the last 4 years, soil samples were taken at 0–20, 20–40, 40–60, 60–80, and 80–100 cm depth to evaluate the effect of N application on soil eutrophication. Fertilization with N had no significant effects on yield, fruit characteristics, and growth of olive trees for the 13 years of study, even when leaf N concentration increased with the amount of fertilizer N applied. Combining soil and foliar application may reduce the amount of fertilizer N necessary to correct a possible N deficiency because our experiments showed this practice to be more effective in increasing leaf N that applying N only to the soil. Our results question the established deficiency threshold of 1.4% of N in dried leaf because no reduction in yield or growth was observed for lower concentrations. However, leaf N concentration did not drop below 1.2% after 13 years with no N application, probably because of N inputs from rainfall and the mineralization of organic N. Whereas under natural conditions of the non-fertilized treatments NH₄⁺–N represented the dominant fraction of mineral N in soil, accumulation of high amounts of NO₃⁻–N in the soil profile occurred in the fertilized plots, which represents a high risk of N leaching from soil. All these results suggest that annual applications of fertilizer N are unnecessary to maintain high productivity and growth in olive. Applying N only when the previous season's leaf analysis indicates that leaf N concentration is below the deficiency threshold, is thus a recommended practice to optimize N fertilization in olive orchards and to reduce N losses by leaching.     

稻草还田模式对稻田土壤速效氮、钾含量及晚稻生长的影响

设计了高桩翻耕抛栽、覆盖免耕抛栽和高桩免耕抛栽3种模式的田间小区试验。结果表明, 不同稻草还田模式对土壤NH₄⁺-N含量影响较大, 对土壤速效钾含量和土壤NO₃^--N含量影响不大; 高桩翻耕模式的土壤NH₄⁺-N、速效钾含量平均值比高桩免耕和覆盖免耕模式分别提高40.8%、7.5%和36.7%、2.0%; 高桩翻耕能促进水稻群体生长, 增加叶片叶绿素含量, 充分利用光能, 增强光合作用; 稻草还田以高桩翻耕模式的增产效果最好, 比高桩免耕、覆盖免耕分别增产5.8%和9.0%。以高桩翻耕稻草还田模式对土壤速效氮、钾含量及晚稻产量的影响最好。     

Long-term effects of N fertilization on cropping and growth of olive trees and on N accumulation in soil profile

Two experiments were conducted for 13 years in two olive groves of southern Spain to study the long-term effect of nitrogen (N) fertilization on trees and soil. In the first experiment, 12-year-old ‘Picual’ olive trees were arranged in a split plot design with method of N application (soil versus a 50% soil:50% foliar combination) as the whole plot factor, and amount of N applied annually (0, 0.12, 0.25, 0.5 or 1.0 kg N tree⁻¹) as the subplot factor. In the second experiment, N application to 50-year-old ‘Picual’ trees was based on the previous season's leaf N concentration. Urea was the source of N in both experiments. During the last 4 years, soil samples were taken at 0–20, 20–40, 40–60, 60–80, and 80–100 cm depth to evaluate the effect of N application on soil eutrophication. Fertilization with N had no significant effects on yield, fruit characteristics, and growth of olive trees for the 13 years of study, even when leaf N concentration increased with the amount of fertilizer N applied. Combining soil and foliar application may reduce the amount of fertilizer N necessary to correct a possible N deficiency because our experiments showed this practice to be more effective in increasing leaf N that applying N only to the soil. Our results question the established deficiency threshold of 1.4% of N in dried leaf because no reduction in yield or growth was observed for lower concentrations. However, leaf N concentration did not drop below 1.2% after 13 years with no N application, probably because of N inputs from rainfall and the mineralization of organic N. Whereas under natural conditions of the non-fertilized treatments NH₄⁺–N represented the dominant fraction of mineral N in soil, accumulation of high amounts of NO₃⁻–N in the soil profile occurred in the fertilized plots, which represents a high risk of N leaching from soil. All these results suggest that annual applications of fertilizer N are unnecessary to maintain high productivity and growth in olive. Applying N only when the previous season's leaf analysis indicates that leaf N concentration is below the deficiency threshold, is thus a recommended practice to optimize N fertilization in olive orchards and to reduce N losses by leaching.     

马铃薯连作地健康株与病株根区土壤微生态特性比较

为探索甘肃省连作马铃薯健康生长的微生态机制,采用常规养分分析法测定了健康株与病株根区土壤中速效氮磷钾含量,稀释平皿涂抹法测定土壤放线菌数量,琼脂块法筛选拮抗放线菌;16S rRNA序列分析法鉴定优势放线菌,发酵液抑菌试验检测优势放线菌灭癌素链霉菌(S. gancidicus)对马铃薯病原真菌的抑菌作用。结果表明,在连作4年的田中：马铃薯病株根区土壤的速效P、K含量分别较健株低29.9%、12.5%,铵态氮含量较健株高24.1%。在高氏1号培养基上,病株根区土壤中放线菌总数、小单孢菌及未鉴定放线菌数量较健株分别减少51.1%、83.0%及53.9%;腐植酸琼脂培养基上,病株根区土壤中放线菌总数、链霉菌数量较健株分别减少46.0%、46.7%。在病、健株根区土壤中,对4株靶标真菌的拮抗潜势SAAP值均病株小于健株。健株根区土壤中的优势放线菌为灭癌素链霉菌(S. gancidicus),该菌对4株马铃薯常见土传病原真菌立枯丝核菌(R. solani)、茄病镰刀菌(F. solani)、硫色镰刀菌(F. sulphureum)及大丽轮枝菌(V. dahliae)均有抑制作用;病株根区土壤中的优势放线菌为加利利链霉菌(S. galilaeus),该菌为马铃薯疮痂病致病菌。由此可知,保持连作马铃薯健康生长的根区土壤微生态特征是,高量磷钾及低量氮的速效养分组合,较多放线菌且拮抗放线菌的拮抗潜势较大,优势放线菌为有益菌。     

Ein Beitrag zur Stickstoffwirkung nach unterschiedlichen Verfahren stabilisierter Klärschlämme*

A distribution to the availability of the nitrogen in sewage sludges stabilized with different processes In two pot experiments the availability of the nitrogen in sewage sludges stabilized with different processes was investigated. Further it was examined whether the Quantofix-N-Volumeter (method for rapid determination of ammonia in slurries) is able to determine the plant available nitrogen in sewage sludge. The following results were obtained: In the experiment where same amounts of total N were applied as sewage sludge a highly significant correlation existed between the amount of NH₄-N applied and the N uptake of the plants. When equal amounts of NH₄-N were applied the N uptake was lowest with the sewage sludges with a high relative part of NH₄-N of the total N (thermophile-aerob; mesophile-anaerob). However the reason for this result was not only the lower application rate of total N with these sewage sludges but also the lower efficiency of the organically bound nitrogen. A very highly significant correlation existed between the application rate of organically bound nitrogen and the N uptake. The values of nitrogen in sewage sludges measured by the rapid method gave information about the plant available nitrogen in the year of application. A close quantitative agreement existed between the available nitrogen determined with the rapid method and the values calculated with the formula of Furrer and Bolliger (1978).     

Yield Formation and Plant Metabolism of Spring Barley in Response to Locally Injected Ammonium

This study was conducted to elucidate the crop physiological basis for yield differences frequently observed in experiments comparing top‐dressing of N fertilizers with injection of ammonium or ammonium/urea solutions into the soil. The effects of diammonium phosphate (NH₄‐N) injected at the two‐leaf stage, calcium nitrate (NO₃‐N) broadcasted and incorporated before sowing, and a control without N fertilization (‐N) were assessed from measurements of growth, N‐uptake and N‐partitioning, light interception, gas exchange, leaf anatomy and the activity of key enzymes of N‐metabolism. The experiment was performed with spring barley (Hordeum vulgare L.) grown in 80‐l containers in a vegetation hall in Braunschweig, Germany. The plants in the NH₄‐N treatment produced a 20 % higher grain yield than those in the NO₃‐N treatment. The grain yield superiority of the NH₄‐N plants was attributable to a higher number of ears per plant (+13 %) and more grains per ear (+6 %). The NH₄‐N plants exhibited lower concentrations of inorganic cations than plants supplied with NO₃‐N. In the NH₄‐N treatment, the light penetrated more deeply into the crop canopy and the NH₄‐N plants exhibited a higher leaf carbon exchange rate at the different leaf layers than the NO₃‐N plants. It is concluded that as opposed to predominantly nitrate nutrition, provision of a persistent source of ammonium enables plants to take advantage of the positive yield effect of mixed N nutrition.     

氮素实时管理对冬小麦产量和氮素利用的影响

为实现氮素效率和小麦产量的协同提高,以山东省泰安市和兖州市为试验地点,连续2年在4个田块上进行了基于土壤硝态氮测试的氮素实时管理试验。与农民习惯施肥相比,优化施氮处理提高产量0.87%～10.44%,平均5.82%;而氮肥用量减少38.61%～53.29%,平均46.70%;氮素吸收效率、氮素表观利用率和氮素农学效率分别增加36.67%～85.69%、58.49%～267.69%和34.16%～410.58%;氮肥偏生产力升高74.23%～124.87%;产/投比提高78.50%～112.09%。说明应用土壤硝态氮测试进行小麦氮肥实时实地管理达到了减少氮肥用量,提高氮素利用效率,增加产量和经济效益的目的。     

Effect of composting on nutrient loss and nitrogen availability of cattle deep litter

Nitrogen and carbon emissions and plant nutrient leaching during storage of solid deep litter from dairy cow houses was examined in this study. Included was an assessment of the potential for reducing emission and leaching losses by compaction, mixing and by covering the deep litter. During a composting period of 132 days from October 1998 to March 1999, emissions of NH₃, N₂O and CH₄ and leaching of nutrients during composting were measured. Denitrification was estimated as N unaccounted for in N mass balance calculations. During mixing of the deep litter, N was lost and the emission and leaching losses during composting were consequently low compared with the other treatments. Covering the compost with a porous tarpaulin or compacting the compost reduced emission losses to 12–18% of total-N compared with a loss of 28% during composting of untreated deep litter. Most of the nitrogen loss was due to NH₃ volatilization; leaching accounted for about one fifth of the N losses and only a little N was lost due to denitrification. Leaching loss of potassium (K) was 8–16% of the amount present at the start of the experiment; compaction and a cover reduced the volume of liquid leaching from the heaps and K loss. Less than 0.3% of the total-N was emitted as N₂O, and CH₄ emission was between 0.01 and 0.03% of the C in the stored deep litter. The yield level of barley was poor in this study and the fertilizer effect of compost was low. The yield response of barley showed that compost had a significantly lower fertilizer efficiency than deep litter applied to the field directly after emptying the animal house.     

Potassium Management for Brown Midrib Sorghum × Sudangrass as Replacement for Corn Silage in the North-eastern USA

In recent years, there has been a growing interest in brown midrib (BMR) sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (SxS) as a replacement for silage corn (Zea mays L.) in the north‐eastern USA. Recent studies suggest it is suitable for both rotational grazing and as a hay crop and could compete with corn harvested for silage in years when wet spring conditions prevent the timely planting of corn. However, little is known about its suitability as forage for non‐lactating cows that require low potassium (K) forages to prevent health problems. Our objective was to evaluate the impact of K fertilizer management (0, 112 or 224 kg K₂O ha^?1 cut^?1) under optimum N management (112–168 kg N ha^?1 cut^?1) on yield, quality and K concentrations of BMR SxS over a 2‐year period. Field trials were established on a fine loamy, mixed, active, mesic Aeric Fragiaquepts with medium K‐supplying capacity and characteristic of a large region in New York. Potassium application did not affect dry matter yields in either of the 2 years. Averaged over 2 years, neutral detergent fibre (NDF) significantly increased with K addition with similar but non‐significant trends observed in each of the years individually. The digestibility of NDF was unaffected by K application. Crude protein (CP) concentrations showed a significant decrease with K application in 2002 and similar trends were observed in 2003, although differences were not significant at P ≤ 0.05. The changes in NDF and CP did not significantly impact forage quality expressed as milk production per megagram of silage. Potassium application increased forage K concentration up to 13 mg K kg^?1 dry matter (in the first cut in 2003). Forage Ca and Mg concentrations decreased with K addition except for the first cut in 2002 where differences between 112 and 224 kg K₂O ha^?1 treatments were not significant. Without K addition in the 2‐year period, K concentrations in the forage decreased from 23 g kg^?1 for the first cutting in 2002 to 15 g kg^?1 for the second cut in 2003. Low K forage was obtained for all second‐cut forage unless 224 kg K₂O ha^?1 cut^?1 had been added. First‐cut forage was suitable only when no additional K had been applied. These results suggest low K BMR SxS forage can be harvested from initially high K soils without loss in dry matter yield as long as no additional K is added.